osf1 man page for sigaltstack

sigaltstack(2)							System Calls Manual						    sigaltstack(2)

NAME
       sigaltstack - set or get signal alternate stack context

SYNOPSIS
       #include <signal.h>

       int sigaltstack(
	       const stack_t *ss,
	       stack_t *oss );

       The  following  function declaration does not conform to current standards and is supported only for backward compatibility: #include <sig-
       nal.h>

       int sigaltstack(
	       stack_t *ss,
	       stack_t *oss );

STANDARDS
       Interfaces documented on this reference page conform to industry standards as follows:

       sigaltstack():  XPG4-UNIX

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS
       If valid, specifies a pointer to a structure that indicates what will be in effect upon return from the call to the  sigaltstack  function.
       If  not	NULL,  specifies  the  pointer to a structure that contains the alternate signal stack that was in effect prior to the call to the
       sigaltstack function.

DESCRIPTION
       This function enables another stack area to be defined where signals can be examined for their execution status and processed.  If  a  sig-
       nal's action, specified by the sigaction(2) function, indicates that a signal should execute on an alternate stack, that signal is examined
       for its processing status.  A process that is not currently executing on the signal stack is switched to an alternate stack for	the  dura-
       tion of the handler's execution.

       The sigaltstack structure is set up as follows:

       void	  *ss_sp     /* SVID3 uses caddr_t ss_sp int	    ss_flags size_t	ss_size

       The  values  for  the fields are: Signal stack pointer.	Specifies the new stack state and may be set to either SS_DISABLE or SS_ONSTACK as
       follows: If ss is not NULL, the new state may be set to SS_DISABLE, which specifies that the stack is to be disabled and ss_sp and  ss_size
       are  ignored. If SS_DISABLE is not set, the stack will be enabled.  If oss is not NULL, the stack state may be either SS_ONSTACK or SS_DIS-
       ABLE.  The value SS_ONSTACK indicates that the process is currently executing on the alternate stack and that any attempt to modify it dur-
       ing execution will fail.  The value SS_DISABLE indicates that the current signal stack is disabled.  Specifies the size of the stack.

       The  value  SIGSTKSZ  defines  the average number of bytes used when allocating an alternate stack area.  The value MINSIGSTKSZ defines the
       minimum stack size for a signal handler.  When processing an alternate stack size, your program should include these values  in	the  stack
       requirement to plan for the overhead of the operating system.

RETURN VALUES
       Upon successful completion, zero (0) is returned.  On error, the value -1 is returned and errno is set to indicate the error.

ERRORS
       The sigaltstack() function sets errno to the specified values for the following conditions: The ss parameter is not a null pointer, and the
       ss_flags member pointed to by ss contains flags other than SS_DISABLE.  The size of the alternate stack area is less than MINSIGSTKSZ.	An
       attempt was made to modify an active stack.

SEE ALSO
       Functions:  getcontext(2), sigaction(2)

       Routines:  sigsetjmp(3)

       Files:  ucontext(5)

       Standards:  standards(5)

																    sigaltstack(2)